1/8 plate can be used for the base but if you happen to have an extra cover for your diff simple torch the outer bolt ring off and build onto that .

Used solid steel rod wich can be bent with a short piece of pipe and heavy hammer to mold the shape you want . Bolt the ring to the diff before welding on the cross parts to make sure the torch has not warped it . If you get done and it wont bolt on your screwed .